Giving 2d contours Z-height from attribute table in QGIS

Question

I have a contour data file downloaded from UK Ordnance Survey, which gives 2d contours of an area in gml format (also supplied in .shp format) with the heights of each contour attached to the attributes of each line.

I want to give the contours a Z value of the height attribute attached to it, so that I have a 3d contour file I can then use in QGIS to create hillside shading etc, and potentially export to dxf/dwg.

Is there a way to do this without manually moving each line?

I was hoping for an actual tool I can use, as I have no script experience.

Answer 1

You don't need to convert your layer in 3D layer to make interpolations, you only need the z attribute.

You can choose between working with the contour lines or with points:

1) with the contour lines:

• you can use the QGIS interpolation plugin to generate a TIN or IDW, but it's better with points

• you can use GRASS GIS r.surf.contour in the processing toolbox

2) with points

You can create points along input lines with GRASS GIS or SAGA GIS in the Processing Toolbox or with PyQGIS in the Python console.

And you can use

• all the interpolation plugins of QGIS: QGIS interpolation plugin, raster interpolation plugin
• all the interpolation modules of GRASS GIS or SAGA GIS in the Processing Toolbox

3D raster in GRASS GIS nviz

Answer 2

It's not necessary to to interpolate your contour shapefiles to obtain data for jobs like making shaded-relief and elevation-coloured layers. The OS OpenData dataset 'Terr50' includes DEMs (Digital Elevation Models) as *.asc files that can be used directly for these purposes.